Most display technologies fool a viewer's human visual system (HVS) into perceiving moving images by showing a rapid succession of static images (e.g. provided in frames) with slight changes between the images. The viewer's eyes will begin to track features in the image that are changing from frame to frame. The tracking typically takes the form of smooth pursuit, where the viewer's eyes follow the approximate path of the object. Because the actual object motion is periodic (e.g. an object only changes positions when one frame is removed and the next displayed), each element within the image is blurred in the direction of motion. The amount of blur is proportional to the time the object is displayed and the speed of the eye motion (which typically matches the speed of the object motion).
Most display technologies also build up each image (frame) over the frame period using successive flashes of light. These flashes may be of varying intensity, varying color and of varying duration. The parameters of the light flashes are controlled by the display (and/or by a computing device controlling the display) to construct the desired brightness and color of each image element (pixel). Where the flashes are closely spaced the viewer perceives blocks of continuous light but for pixels with less than maximum intensity there may be a gap with no light before, after and even within the main block of light. When the gaps are before and after the light, the image can appear to flicker at the frame rate. For common displays operating below 75 Hz frame rate (for example, at 24, 30, 50 or 60 Hz) this can fall below the flicker fusion threshold of the viewer, resulting in flicker artifacts.
One solution to the problem of blur is to display each image for a shorter period of time. Unfortunately, reducing display time reduces display brightness and tends to create a flicker artifact perceivable by the viewer when the frame rate is below the viewer flicker fusion threshold. Common displays operating below 75 Hz (for example, at 24, 30, 50 or 60 Hz) would suffer from this problem without the adoption of multi-flash or multi-draw approaches.
Another solution to the problem of blur is to filter the incoming image into two or more images and then display each image for a shorter period of time. Moving object detail is typically displayed for a much shorter time. Unfortunately, filtering the incoming image to detect motion introduces additional latency and the reduced display time of the detail frames can introduce other artifacts such as brightness variations.
Another solution to the problem of flicker at low frame rates is to use multi-flash and/or multi-draw approaches. Multi-flash (multi-draw) technologies reduce the risk of viewers perceiving flicker artifacts by breaking the block(s) of light used to build (draw) the image into more than one block (flash). This pushes the flicker frequency to at least twice the frame rate, well beyond the typical human flicker fusion threshold. Unfortunately, multi-flash/multi-draw displays introduce a multi-draw artifact when the viewer is tracking moving objects within the image. Instead of simply blurring, objects appear to multiply in the direction of motion. For example, one tower can appear to become two towers, the letter V can appear to be the letter W, etc.
Yet a further solution to both the problem of blur and flicker is to increase the frame rate. Unfortunately, increasing frame rate requires additional image data to improve blur (otherwise it is simply multi-draw), and this additional image data requires either: a. interpolation between frames, which adds latency to the display and also exhibits other artifacts such as improper interpolation (algorithms misinterpret which objects are moving where) and improper reveal (algorithms replace moved objects with incorrect background images); or b. investment in additional data capture/processing/playback/generation equipment such as cameras or rendering computers.